Field of the Invention (Technical Field):
The present invention relates to an energy harvester comprising a mass that subjectable to environmental forces for bringing it into the status of a moving mass.
Description of Related Art:
In the last decade, the field of energy harvesting has increasingly attracted interest and has gained on importance as evidenced by the growing number of publications and product prototypes. Generally speaking sources for energy harvesting are available in four forms: light, radio waves, temperature gradients and motion. Outdoor solar energy provides a power density of about two orders of magnitudes higher than other sources. However, solar energy is not an attractive energy source for indoor environments. Particularly for indoor application kinematic energy is considered to be an attractive option.
Energy harvesting from for instance ubiquitous environmental vibration and human's everyday movement or other types of movement, particularly but not exclusively by micro-electronic-mechanical systems (MEMS) technology appears to be a promising source of power that can be used for portable devices and wireless sensors networks. The vibration or movement coming from the environment can be converted to electric energy using three types of electromechanical transducers: electromagnetic, electrostatic, and piezoelectric or stored in the form of strain energy for later use.
The article ‘Energy-harvesting device with mechanical frequency-up conversion mechanism for increased power efficiency and wideband operation’, by Seok-Min Jung and Kwang-Seok Yun, Applied Physics Letters 96, 111906(2010) discusses an energy harvesting device that uses snap through buckling for a mechanical frequency-up conversion. The proposed device consists of buckled slender bridges with a proof mass and cantilever beams attached on them. This improves the usable bandwidth of the device.
The article ‘Experimental investigation of a post-buckled piezoelectric beam with an attached central mass used to harvest energy’, by A J. Sneller, P. Celle, and B. P. Mann, Proceedings of the Institution of Mechanical Engineers, part Journal of Systems and Control Engineering 2011 Volume 225, pages 497-509 investigates the response of a buckled piezoelectric beam to harmonic base excitation. This study reports on the effects of an attached mass on persistent snap through behavior, which has clear applications to energy harvesting due to its relatively large amplitude motion.
The article ‘Bidirectional frequency tuning of a piezoelectric energy converter based on a cantilever beam’, by C. Eichhorn, F. Goldschmidtboeing and P. Woias, Journal of Micro mechanics and Microengineering 19, 2009, pages 1-6 reports on the tuning of the resonance frequency of a piezo-electric energy converter by applying mechanical stress to its structure.
The article ‘Temperature Compensation in Piezoelectric Energy Harvesters Using Shape Memory Alloys’, by Mohammed Rhimi and Nizar Lajnef, Proceedings of SPE, volume 7981 798139 1-9 discusses that harvested vibration energy is typically considered as an alternative power source for sensors' networks for health and usage monitoring in civil and mechanical structures. The article discusses the effects of temperature deviations on the theoretical harvestable energy levels as well as the compensation methodology.
The article ‘Towards an autonomous self-tuning vibration energy harvesting device for wireless sensor network applications’, by Vinod R. Challa et al, Smart Materials and Structures, IOP Publishing Limited, Bristol, GB, volume 20, number 2, 25004 discloses an energy harvester comprising a mass that is subjectable to environmental forces for bringing it into the status of a moving mass, and a piezoelectric cantilever linked to the mass for converting and storing of energy embodied in the moving mass, which means are arranged for subsequent release of said energy.